Single channel radio communication system affording break-in operation



June 7, 1949. w. D. HAlLl-:s 2,472,585

` SINGLE CHANNEL RADIO COMMUNICATION SYSTEM AFFORDING BREAK-IN OPERATION Filed April 4, 1945 2 SheejZs-S'heell 1 s l Q N J N N l l f s V Q: *u u li u w w i i E A n Bnventor 8g WM j (Ittor'neg June 7, 1949. w. D. HAlLEs SINGLE CHANNEL RADIO COMMUNICATION SYSTEM AFFORDING BREAK-IN OPERATION 2 Sheets-Sheet 2 Filed April 4, 1945 AIM/x @ld M m .GE

Patented `fune 7, 15949 SINKrLlI CHANNEL RADIO COIVIlvIUNICAlIONA SYSTEM' AFFORDING BREAK-IN OPERA- TION 'Willamf D; Hailes, Brighton, N. Y., assignortol VGeneral' Railway Signal Company, Rochester,

Applictionv-April 4, 1945, Serial N0. 586,599

i 17-V Claims.

l. This inventionrelatesto communication systems' for transmitting intelligence verbally v or otherwise -loyy modulationl o'i a carrier. frequency,

and? more particularly*4 pertains-itc` su'ch 4 a communication system adapted -fory use infconnection `with' communication with and. between Y mobile nection withspace radiation asl-inthewusual radio system, or by induction intolineewirea track rails,

or'like conductors' along the path'l'of'movement of the mobile unitin-a manner: co'mmonly'refeired to as awired `.raclio or carrier" current system. It is further contemplated that itwill ordinarily be desirableto' `provide for-two-Wayffcommunication between" the mobile unit andanotherU station located valong-y the' wayside over'` the same-carrier frequency channel.

Fonexample'; when aradio-ltelephone' system is employed for issu-ing instructions" tora'f pusher engine moving4 carsfoveritheli-ump.`I in a ,classification yard on a railroad, it is essential for the Asafety of the locomotivelthatth'e way-side operator can instruct the engineer` immediately `as to any troubleoroccasion-that-the train` should be stopped;` but in atwo-way 'systemloff communication on thesamechannel; it'is'de'sirable to provide interlocking means which? allows transmis- Asion from one station to 'lock outr the`other stationuntil the rs'tst'ation has-"stopped its-communication. This is because the rst station cannot receive'- until it stops 'transmitting any.- lway, so that it' is Adesirableto preventfthe lsecond station operator from falsely' thinking that he has successfully transmitteclhis message. `With such an organization, it is apparent'that the Wayside Voperator might hai/e'fiinportant instructions to transmit but' Would/be "withheld-from doingit by reason of the monopoliaation ofthe communication rchannel by -anoperator 'on'a' pusher engine, or -by reason off the ffactthat several engine stations mightfgainyaccess tof the channel successively in such a way-astolpreventf the transmission of the" important instructions' from the wayside'.

The present inventionris not'lorilyv adapted to provide the characteristic featuresof the present invention '1in-'- connection'i with communication "between a mobileiunit an'da YWayside" station; but

lli:

f2 thevinvention 'mayi also rbeapplied-to commun-ication between two or more mobile units, orffbetween one lend vof a mobile unit'and-the otheriend such as` between ythe rearfemi of a. train and-its locomotive. In this lastcase, itfm'ayf be fdesirable to provide that each stationV beallottedonlyta particular period-of timeforcommunication so that 4the stations may' transmitfalternatelywithout `either being` superiory to lthe other.

In viewJ ofthese considerations, it isi `proposed to provide a communication vsystemiin vwhich two- Way communication is provided on the samefrequency: channel withlan interlock toallowfone station to transmit' and hold out fthe'- Otherstation for only a-limited` time and then4- give4 asimilar opportunity-for transmissionffrom any other'A station. In other-words; each stationfisfgivenialimited time in which to transmit and then a'turnito transmit'is provided` another station.' Inf this way, communication of messages between any1" two Istations mustf be effected' alternately-at spaced intervals if both stations-1are endeavoring: to transmit at the' same time.- However-,rif only one stationL is Iendeavoring:tovtransmit, it can fdo so'- as long'as desired but suchtransmissionwwill be periodically: interrupted .by yshort intervals-:or break-in periodsduring "which, another :station can -gain control of the'fc'arrier frequency-channel if' desired.

In 'some cases' it maybe desirable-to renderorie station superior to another, sothat itWi-ll=not l only be' abley to-"br'eakf into Athe communication channel, but 'may also `be"' superiori in .f the sense that-it` can continue lits transmissionQ as-"long'- as desired. Thus; itisr'pro'posed `to prov'idefal twoway communication system' f in kvwhich' .the f `automatiobreak-in featureisi applied to only oneV of tw'o stationsfleavingr a'main or piimaryrstation independent of anautomatic break-in and allow it to continue vto transmituas' long asfdesiredl and withhold -f the automatic" characteristics of="-the other station or stations.

Another f feature 2 of the' present l invention-is that one or more'fstations Imaybefprovidedfyvith what is calledv a: program' vsequencingfdevice lso that 1 a stationy may i transmit long; messages-or short messages with suitable `V'intervals between the 4'messages in -accordancewitha predetermined `program or-allottment-of times-*forv transmission and reception. In this `way., itis/believedf that communication between aA plurality.. of .different stations can be-most readilyJ adapted to the practical problems of y, communication in connection with moving-vehicleswhich:atall times must be *assuredA of reception-of vtheir instructionsjbe'- cause the stations may be provided with what may be termed automatic break-in facilities so that such stations cannot monopolize the communication channel to the exclusion of other stations. These break-in features may be organized to give any desired station a superiority with respect to the others or all stations may be given equal rank.

Other objects, purposes and characteristic features of the invention will be in part apparent and in part pointed out as the description of the embodiment of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which two specic forms of the present invention has been illustrated in a simplified and diagrammatic manner, and in which- Figs. 1 and 2 represent two typical stations providing two-way communication on the same frequency channel with the automatic break-in features of the present invention applied thereto; and

Figs. 3 and 4 illustrate another form of automatic break-in features applied to a single station as typical of a plurality of stations and associated with the superior station of Fig. 3.

1n order to simplify the illustrations in the drawings and facilitate the explanation of the fundamental characteristics of the invention, various parts and circuits have been shown diagrammatically in accordance with conventional symbols. Arrows with associated symbols (-1-) and are employed to indicate connections of the circuits to the various relays to the opposite terminals of a suitable source of current for the energization of such relays, and the source of current may be of any suitable characteristic for the purpose intended. The various contact fingers of the relays are shown conventionally as being in a lower or inclined position when the coil or winding of the associated relay is deenergized, and in a raised or horizontal position when the relay is energized; the contacts belonging to any given relay are shown connected to its coil by dotted lines and these contacts may be either below or above the illustration of the relay winding. The front and back contacts operated by the different relays are shown conventionally as arrowheads, which contacts are ordinarily of the type which have their contacts biased downwardly by gravity or by spring action.

The specic embodiment of the invention chosen for the purpose of illustration and description comprises a radio telephone communication system of the usual and Well-known type, employing either amplitude or frequency modulation and operating on a suitable carrier frequency allocated or the particular use; and in connection with the control of traffic it is contemplated that such frequency channel will be in the megacycle band. Since the structure and operation of radio telephone transmitters and receivers are well known in the art, no attempt has been made to illustrate the various component parts such as oscillators, intermediate frequency ampliers, power ampliers, modulating and demodulating circuits, emphasis and pre-emphasis organizations for frequency modulation or any such other components as may be required for the particular radio characteristics desired, it being assumed that any conventional form of circuit arrangement may be used and this has been represented by rectangles designated Transmitter and Receiver for each of the stations illustrated.

Automatic break-im. features for a plurality of stations-With reference to Figs. 1 and 2, each gure represents a separate station which may be located on the wayside or at some locations on a mobile unit, and each station is provided with a suitable Transmitter and Receiver. With more particular reference to Fig. 1 as typical, it will be seen that the Receiver of the station is normally connected to its associated antenna through back contact 5 of relay ITR; but when the relay ITR is picked up, it connects the antenna to the Transmitter- Similarly back contact t of relay ITR normally connects the plate supply (or B battery) to the Receiver to render it active for the reception of carrier frequency signals, but when the relay ITR is picked up front contact 6 connects the plate supply to the Transmitter. Both the Transmitter and Receiver are provided with their respective ground connections, and are assumed to be of any suitable type either of the amplitude or frequency modulation types, but adapted to receive and transmit the carrier frequencies suitably modulated. The receiver is provided with the usual loudspeaker ILS; while the transmitter is provided with the usual microphone IMK.

Associated with the Receiver is a carrierresponsive relay ICR. This relay is normally deenergized even though the associated receiver is rendered active by reason of the connection of its plate supply, but whenever a carrier frequency signal of the proper frequency is received, the carrier-responsive relay ICR is picked up irrespective of whether or not such carrier frequency signal is modulated with a Voice message, or other form of intelligence. This carrier-responsive relay ICR may be energized in any suitbale way, one way may be as shown in the prior application of Knapp and OBrien Ser. No. 565,206 led November 27, 1944, now Patent No. 2,435,010, dated January 27, 1948.

The transmit relay ITR has associated therewith a repeater relay ITRP which is slow in picking up and considerably slower in its releasing characteristics. The transmit relay ITR is preferably quick in picking up but somewhat slow in releasing. These pick-up and release characteristics will be considered more in detail hereinafter.

The station of Fig. 1 includes a push-to-talk button ITB and associated indicator lamps to indicate when the station is receiving, when a breakin period is to occur and when the operator may talk, which indicators are designated IRK, IBIK and ITK respectively. A single stroke warning bell IBR is provided to give a warning Whenever the station is to receive a message during a breakin. pericd and thus advise the operator that he may expect to receive a message rather than to prepare to continue his transmission at the end oi the break-in period.

Both of the stations shown in Figs. 1 and 2 are similar, and the various devices have been given the same letter reference characters, with preceeding numerals characteristic of its gure numbers; and in this connection it should be understood that there may be more than two stations associated in a group but for convenience in the description only the two stations shown will be taken into consideration.

Whenever the operator of the station in Fig. 1 desires to transmit a message, he actuates the push-to-talk button ITB and thereby closes a circuit from through back contact 'l' of button ITB, back contact 8 of relay ICR, front contact 9 of relay ITRP, windings of relay ITR to S This energiza-tion of the relay-l1 'IRcauses-itsfcone taets-todmmediately pick up and'frenderl the-staf tion in conditionfor. transmissionof: a voice message.

It Willbe-notedthatthe repeater relayt ITRP is normally energized through back contact I 'of the transmit -relay ITR; and vis deenergizedso that it-'Will release after a time' Whenever the relay ITR-is picked up. As soon as the relay ITR. picks up, it closesfront contact Illv and'energizes the taiklamp ITK. This'advises the operator that the-'system is readynfor transmission and that he may talk into the microphone IMK to .transmit hismessage.

T hotransmission of a-message from the.- stationofgFig. 1 is 4eected by'fthe radiation of the modulated carrier frequency from -theassociated antenna, and -is received by one-or more -associatedstations such as shown in-'-Fig.'2 -for example. Thisis because the Receiver of Fig. 2"is normally rendered active by reason'of the closed condition ofk back contacts Hand I2 of its transmit relay-ETR. The reception of the carrier signal atgthe station of Fig. Z'results in the energization of its carrier-'responsive relay 2CR which opens backcontact I3 to prevent the energization of the transmit relay ZTR in the event that the operator at the station of Fig. 2 should actuate the pushfto-talk button ZTB'during the reception of such message. The closure of front contact I dof relay ZCR. causes Ythe'energization of the receiving lamp ZRK advising-theyoperator at the station of Fig. 2 that a message is tobe received.

It will be. seen that as soon as the transmit relay. ITRof Fig. 1 is energized, the relayv ITRP begins its release period which may be of any desired 'length' in accordance'with 'What might'be considered the average length of message transmission, and this may range from veito'iteen seconds or even as long as five minutes if the application of the invention to actual conditions should indicate such a'time to be desirable. In this connection, it maybe that specialtimng apparatus may be required in placeLof a simple slow-acting relay, suchas'indicated by ITRP,'in order ,to obtain the desired length of lmessage transmission period fortherelatively'long times (seeFig. 4); Insome circumstances, it 'may be desirable to provide a very shortbreak-inperiod and` accompanied by a similarly short message period with a complete messagebeing broken up into parts and transmitted during successive message.. periods.

In Yanyevent,after.a time (as selected inaccordance with the particular application involvedytherelayy ITRP releases and opens its front contact 9 eiecting` the deenergization of the. relay ITR. The closureofback Contact I causes the illuminationofthe breakfin warning lamp. IBIK advising the ,operator lthat the break-v in .period is about to take place, and a moment orl two later the actual vbreak-in occurs .when thel transmitrelay ITR. drops away, The warning period may,l be considered as` the durationvofthe release period of the transmit relay ITR, and the length of this period may be suitably selected to allowv completion of a word, or the like.

If the operator at the station of Fig. 2 desires to transmit a message in4 response tothe ,message. being received, he `can actuate his push-totalk .button ZTB even duringthe reception of a message so that assoon as the,-,break'in period occurs at the transmitting` station,his station immediatelyeiects the energizationof the.y relay ZTHWhich turn'causes the radiationY of 'a' car rien signaitoiefectf me .pickingfupioifthewear rief-responsive relay ICR. This'zsopens'backI-con tact il toprevent the operator offthe'stationfiat Fig. 1 from gaining control to vagainftransmit -until after theeallotted time fory the-'- station --of Fig. 2 The `picking upA of f the carrier-responsive relay f ICR oil coursecenerg-izes 1 the-f receivingindicatorVv lRKL through front Contact |64- advising the-'operator to prepare-to receivev'The iactthat the transmit relay 2TR is `effective-atfthestation offFig. 2 isindicated by the illumination' of" the talk lamp/TEK which ist energizedr 'throug-l'ififront contact I1 fof relay 2TH-,l

Sincel the 1relay i ITRP isy deenergized to=-eiect therbreakfsin, its back contact I8`isc1osed-`-W1'1eu the carriereresponsive relayl- IGRI picks upinfr'espense tothe reception of-a carrierisignalfrom the'other station. This-causes-a singleestroke warningby the'ioell l IBRfthat a messageeis'fto'ebe receivedyan'd this occurs'at the same instantthat thereceiving' lamp IRK isenergized.

`After `a suitable interval of'time,"thefrelease of the relay ZTRP'occurs and opensfrontoontact 20 to cause the-break-in' on thel transmission'iirom the-station of Fig. 2,` thev same as'describedirr connectionwith the-'station off-Fig. 1; 1Thus,i:if the stationof Fig. 1 still`desires'totransmit;A then therpusheto-talk `button ITB *is being `held down and the relay ITRP is-of course picked up shortly after-the relay ITB.'y has released, so thatithe transmit relay ITB, Jcan' be energized-during the break-in kperiod provided' upon lthe lrelease iofffthe relay ZTR whichfof course deenergizes 'the relay.; ICR.

From the ,above description, it will be seenth'at the two stations areprovided4 with' alternate talk andreceiving periods. The talk period of a stas tion extends throughoutthe time that the'relay lTRfor example is picked up i. e'; as soon'asit is pickedup' .and until its contacts vacttially'release; Whileits receiving period' is determinedrby the length of the' talk period measured at thepar-i ticularstation which isk transmitting to it, asfor example .the station of Fig. 2.

If "the station of Fig.; 1 for 'example p isl transmittingand desires totransmit a prolonged'rnese sage whichwill'requiremore' than one talk'pe" riod, `thenit transmitsuntil the end-of "oneitaik period which is Whenthe relayiTRreleases;but the release of relay ITR closes Hback contact`=Ill andenergizes ,the relay ITRPto again effectthe energization ofthe relay ITR if the push-toetalk button ITB is stillactuated. Inother words; as tbeoperatorholds down the push-toetalk button l'TB, there is a succession of talkiperiods'spaced by what jmay be termed "break-in periods Vand these Abreak-in periods' are iortlie` duration lofthe picking ,up of the relayA ITRP. This pick-up pe' riod may be relatively` shortsuch as inthe'ordr of one `to-iiveseconds.forexample and 'iftlie period 'is notmore than one "or'twoseconds',f"th`e break-in will. not be objectionablei'for'the'trans mission 4of a prolongedirnessage since "these periods if properly spaced willv be useful for the operator to take a'loreatli;y soto speak,A so asfto continue his message. However, one or' two'sece onds will be adequate for a signal vto be initiated from some other station, such asthestationin Fig..`2, to effect a break-'in upon the message being 4transmitted from the station of4 Fig. 1i

in ,a communication systemv employing stations as .disclosed in Figsgl and 2,.there are-various combinations in .which such stations "may ble used. "For example, it may 'be that vtwo stations such as shown in Figs. 1 and2 are-'located-'owthe 7 front and rear ends of a train, or one station may be located along the wayside and another station located on the train. Irrespective oi the particular location of such two stations, it will be apparent that each station may break in upon the transmission from the other station so that each may transmit alternately with such periods of transmission not exceeding a predetermined time. In such a case, both stations may be said to have the same rank.

On the other hand, there may be a larger number of stations involved, and in such a case no one station can transmit longer than the period measured by its break-in apparatus; and any one of the other stations of the communication system may break-in upon the station then transmitting at the next break-in period.

A further organization of a communication system may involve one or more stations as shown in Fig. l for example with another station such as shown in 3 where no automatic break-in apparatus is employed. The elimination of the automatic break-in apparatus causes the station of Fig. 3 to act as a superior station, that is, it

can initiate transmission of a carrier signal dur- H ing a break-in period, and once its carrier signal is eiective to pick up the carrier-responsive relays at the other stations, it can continue transmission so long as the operator depresses the transmit button 3TB. As shown, the station of Fig. 3 includes a back contact 32 of the carrierresponsive relay SCR, so that the carrier signal can be initiated from this station of Fig. 3 only during a break-in period when another station is transmitting, it of course being understood that if no station is transmitting this station of Fig. 3 can transmit at any time. However, it can be seen that once this station initiates transmission that it will continue until the button 3TB is released. In some cases, it may be desirable to omit f the back contact 32 and permit the station of Fig. 3 to initiate transmission at any time instead of waiting for a break-in period. In brief, one combination of stations contemplated by the present invention may be considered as including stations l, 2 and 3 used in combination with the station of Fig. 3 acting as the superior communication station.

With more specic reference to Fig. 3, the Receiver is normally rendered active by reason of back contacts 3B and 3l of the transmit relay 3T3, but when the push-tc-tal. button STB is operated, the transmit relay STR is energized through back contact 32 of the carrier-responsive relay `SCR so that the Transmitter is then rendered effective for control by the usual microphone SM'K. The Receiver is provided with the usual loudspeaker SLS. Whenever the carrier-responsive relay SCR, which is responsive to the reception of a carrier signal by its associated receiver irrespective of the presence or absence of modulations, is picked up, it closes front contact 33 to cause the energization of the receiving lamp SRK. Also, when the transmit relay 3TR is picked up and closes front contact 34, the talk lamp STK is energized.

As mentioned above in connection with Figs. 1 and 2, it may be desirable to provide longer message periods than can be conveniently measured by a single slow-acting relay or several slowacting relays in cascade, and in such cases a motor-driven timing organization may be used. As typical of such an organization, Fig. 4 has been shown representing a station as having what may be termed a program wheel which is motordriven to provide the automatic break-in periods at deinite time-spaced periods. It is to be understood that this modified fonn of Fig. 4 may be used in place of stations such as shown in Figs. 1 and 2, and that such a station as shown in Fig. 4 may be used with another like station; with a plurality of like stations; with a superior station as shown in Fig. 3; or with a plurality of like stations and a superior station as shown in Fig. 3. These various combinations of station arrangements are of course dependent upon the particular situation with which the present invention is to be used.

With reference to Fig. 4, the Receiver is normally active by reason of the closed condition of back contacts ill and 4|; but the Transmitter is rendered active Whenever the transmit relay llTR is picked up. The Receiver is provided with the usual loudspeaker GLS; While the Transmitter is provided with the usual microphone 4MK. This station is provided with a push-to-talk button 4TB., a carrier-responsive relay iCR, which is responsive to the reception of a carrier signal irrespective of the presence or absence of modulations, a transmit lamp 4TK, a receiving lamp RK, and a program sequencing organization.

The program sequencing organization includes a motor 4M of any suitable type which is set into operation whenever the push-to-talk button 4TB is actuated and back contact 42 is closed. When the motor 6M operates, it actuates either directly or through suitable gearing, a control Wheel 4CW which is notched and has an associated contact 43 which is intermittently operated to its opposite positions as the control wheel 4CW is rotated by the motor 4M. The contact 42 as Well as supplying energy to the motor, supplies energy to the contact 43 which in one position energizes the slow-release relay 4X and in its other position energizes the slow-release relay 4Y. When the control wheel 40W is being rotated by the motor 4M, the application of intermittent pulses to these relays 4X and Y by the operation of the contact 43, causes these relays 4X and 4Y to be picked up and to maintain their contacts closed even though they are only intermittently energized. When wheel llCW is not in operation, contact 43 remains in one position or the other.

The operation of the program organization by the motor 4M causes the program wheel 4PW to be operated. This is a cam having the desired shape to cause the desired operation of the contact 44. Assuming that the push-to-talk button 4TB has been operated, then the beginning of the rotation of the program organization has the result of the energization of the motor 4M, causes the picking up of the relays 4X and 4Y so that energy can flow from through contact 44 in its raised position, operated contact 45 of the button GTB, back contact 4G of relay lCR, front contact 41 of relay 4X, front contact 48 of relay 4Y, windings of relay 4TR, to This energizes the transmit relay 4TR and renders the transmitter active. This is indicated because the closure of front contact 49 energizes the talk lamp 4TK advising the operator that he may transmit his message through the microphone 4MK. As the program organization operates, the program wheel 4PW operates to a position in which a break-in period is to occur and the contact 44 assumes a lower position and energizes the indicator lamp 4BIK advising the operator of the station at Fig. 4 that a break-in period is to occur which will exist as soon as the relay 4TR reenvases 9 leasesiandiwill be indicated bythe extinguishing of the talk lamp Hli'llK. In 'other lWords,theWainingrperiod is Ameasured by the` release period of the relayfllTR.

If another 4station such as the superior station ofFig. 3 desires'to'transmit a message, itdoes'so in the usualway by the lactuation of the push-totalk button STB which transmits a carrier frequency signal that is received by the station of Fig. 4 energizing the carrier-responsive relay lJCR. Such energization of the carrier-responsive relay CR prevents the-transmission from the station of Fig. 4 even though the operator maintains the `button ATB actuated. So longas the carriere responsive relay CR is maintained picked upb'y reason of the reception fromA the superior station of'Fig. 3, the station of Fig. 4 cannot transmit; but the cessation of a'message from the station of Fig. 3 will permit lthe station of'Fig. 4to again transmit.`

Whenever the operator actuates `the button TB and initiates operation ofthe motor' 11M, the normalizing cam 4N moves out of its normal position and allows Ithe yback contact Slito 'be closed. Thus, it can be'seen that the motor lM receives'energy to causey at least one complete revolution of the-program vwheel LiPW foreach operation of button ATB; and, when its normal position-has been reached, the`contact "50 will be re-opened .and the motor AM will cease its' operation. L1 other Words, if `the operatormer'ely transmits a short message, the release of the lbutton ATB will-allow the transmit relay TR to release and render the -transmitter'inactive but the motor M continuesoperation'and restores the program Wheel APW to its-normal position in readiness for another operation. In this way, the transmission or message period upon each initiation of the program wheel is assured of being the desired-length or duration; y

In the event that no other station has a` mes-l sage to transmit and thus does not breakinupon the station of Fig. 4 during a break-in period, the operator of the station of Fig; 4 may continueto transmit messages in successive message periods;` To do this,-he merely maintains the push-to-talk button -d'IB actuated and thus continues-to keep the transmitter effective except during-the'breakin periods provided when the program wheel/iPW opens front contact dll-and allows the transmit relay dTRto release.

It should be noted that'the depression in the program'wheel PW includes asuiiicient amount of its 'periphery so that #the front Contact i4 rwill be opened long enough to allowithe release of the relay. 4TH, for a break-in period, No'eiort has been made to vshow specic relationships be' tween the speed of the motor 4M and the speed of the cam wheels 4PW, 4CW-and -!-M,`it being understood that the relative 'speeds of operation canfbe suitably chosen in accordance with the time periods to be measured. If 4different time measuring istov-be used atdiierenttimes the-gear ratio between the motor 4M and the shaft S driving the cam wheels can be suitably7 varied or changed.

It willbe noted that the relays 4X and 4Y are not-'both energized unless the program wheels are actually operating byv the -motor 4M, that is, should the motor `liM -fail to operate due to a broken-circuit or the like, the program `'organiza-- tion "might stop in a 'particular position andenergize either the relay :1Xl or'the'relay -4Y (assuml ing button 4TB tofbe depressed'kbut Whenthus stoppe'd A`it could not energize both. of these relays.

l0 Thus, rtli'e'se relays"V provide? a 'feheckr that the 'program wheelsorg'anization'is operative whenever buttn'iliTB' is actuated.'

It'willbe'hoted that-whenever the motor M is driving the shaft-S,-'and back contact 50 is close'd, it -applies'er'iergynotbnlyto the motor 4M butlalso to the heel" of' contact 43 "so' that the relays '4X land @Y vare intermittently energized so longs-as'thetiming'organization isV in l operation even-ethough-'the buttony ITB is ynot actuated. This'provides that front contacts 4T and 48 will be closed under such circumstances so that shouldfthe -push rbuttcnf-IITB beimmediately re# Jpveratecl;` the immediate energization of 4relay 4TH, woulditake place andthe operator could immediately vtransmit. It-is, of course,- understood thatunder suchcircumstances, theoperator must vbe readyfor a breakein-period to be indicated bythe lamp fiBIK at any time, since under 'such veircuifnstances the program wheel QPW- has not startedfrom its initial position. However, `it is thouglt'that once an operator becomes accustomed -toft'h'euse v=of av system organized in Aalf'cordanc'e -with the presentinvention, he will beY prepared to' stop his lmessage immediately -upn'rth'e-indication of a break-in period, and to continue itas' soon as' the break-inperiod is 'over assuming of 'coursethatsome other sta-l tion has not taken "control ofthe communication channel. l

Having thus shwn a communication system With'sever'al form's'of automatic break-in means, it "isdesire'd-to be understood that these forms `are selected merely to facilitate in the disclosure o-f the invention ratherthan to limit the number of forms which it mayassume; and, it is `to be further understood that various-modifications, adaptations and alterations may be appliedto the spec'iificforms shwn vto meet the particular requirements of yp'ratice withoutinany manner departingfromthe spirit j or scope of the present inyention'except as limited by vthe appended claiisj wiiatii claim is: Y y

1. In' a" communicationsyste'm. for transmitting messages by the modulation of .a carrier -frea (ingr-wy, a `station having areceiver and a transmittfer bothfbeing capable "of operating on the same carrier frequency ,circuitmeans at said stationjfr". normally rendering thel associated receiver eiectivefto receive "carrier signals, Vbut acting qi'nresppse to manual, central to render saidtransmittelractive and said receiver inactive, andrneans set'finto'operation by manual control of'said circuit'meansfrvautmaticaily acting to intermittently render said ltransmitter momentarily'inactive "at spaced intervals regardless yof thi'e' ycontinued':manualcontrol 'of said circuit means.'4 Y y 2. In "a communication "system for transmitting messagesfby the modulation of a carrier freqlincybetvveen aplurality offstation's each havli rendering said manually operable means inef fective so long as such carrier signal is received, whereby any transmitting station can be interrupted by another station in case it has a more important message to transmit.

3. In a communication system for transmitting messages by the modulation of a carrier frequency between a plurality of stations, each having a receiver and a transmitter, relay means normally acting to render said receiver active for the reception of carrier signals, circuit means being manually controllable to energize said relay means to render said transmitter active and said receiver inactive, and a program device set into operation simultaneously with the energization of said relay means and operating to intermittently open said circuit means to render said transmitter ineective and said receiver active regardless of the manual control of said circuit means.

4. In a communication system for transmitting messages by the modulation of a carrier frequency, a plurality of stations each having a receiver and a transmitter, a carrier-responsive relay at each station associated with the receiver at that station and responsive to the reception of a carrier frequency irrespective of its modulations, a transmitter relay at each station normally rendering its receiver eiective to receive a carrier signal but acting when energized to render its associated transmitter effective to transmit a carrier signal, manually operable means at each station for energizing its associated transmitter relay only when the associated carrier-responsive relay is inactive, and control apparatus rendered effective by the manual actuation of said manually operable means for automatically deenergizing said transmitting relay after a time interval independently of the operated condition of said manually operable means, said control apparatus being automatically restored by the deenergization of said transmitter relay. whereby transmission from each station while the manually operable means is actuated is intermittently interrupted to permit some other station to breakin.

5. In a lcommunication system for transmitting and receiving messages by the modulation of a carrier frequency, a station having a receiver and a transmitter, a transmit relay at the station normally deenergized and acting to render the associated receiver active for the reception of carrier signals and the associated transmitter inactive but effective when energized for rendering said receiver inactive and said transmitter active, said transmit relay having slow-release characteristics, a normally energized timing device deenergized upon each energization of said transmit relay and eiective a predetermined time thereafter to open a timing contact, a carrier-responsive relay associated with said receiver and energized upon the reception of a kcarrier signal independently of its modulation, a manually operable contact, an energizing circuit for said transmit relay including said timing contact, a back contact of said carrier responsive relay and said manually operable contact, an indicator lamp energized whenever said transmit relay is energized to indicate when said trans-f mitter is rendered active for the transmission of a message, and another indicator energized whenever said timing device has measured said predetermined time to thereby warn the operator that the transmitter will be rendered ineiective' after a short period measured by the release of said slow-release transmit relay.

6. In a communication system for transmitting and receiving messages by the modulation of a carrier frequency, a station having a receiver and a transmitter, a transmit relay at the station normally deenergized and acting to rend-er the associated receiver active for the reception of carrier signals and the associated transmitter inactive but effective when energized for rendering said receiver inactive and said transmitter active, a normally energized timing device deenergized upon each energization of said transmit relay and effective a predetermined time thereafter to open a timing contact, a carrierresponsive relay associated with said receiver and energized upon the reception of a carrier signal independently of its modulation, a manually operable contact, and an energizing circuit for said transmit relay including said timing contact, a back contact of said carrier responsive relay and said manually operable contact.

7. In a communication system for transmitting messages in both directions between different stations by the modulation of the same carrier frequency and each of said stations having a receiver and a transmitter, a transmit relay at each station normally rendering the associated receiver active for the reception of carrier signals and said transmitter inactive but acting when energized to render said receiver inactive and said transmitter active, a timing device set into operation each time said transmit relay is energized and having a timing contact opened alter a predetermined time, a carrier-responsive relay associated with said receiver and energized whenever a carrier signal is received, a manually operable self-restoring push button, and a control circuit for said transmit relay including said timing contact, a back contact of said carrier responsive relay and a contact closed upon actuation of said push button.

8. In a communication system for transmitting messages in both directions between two stations by the modulation of the same carrier frequency, each station having a receiver and a transmitter, automatic break-in means at one station but not at the other station rendered elective by manual control for communication to the other station to cause that one station to be temporarily conditioned for receiving at spaced time intervals each long enough for transmission of a short message, a carrier-responsive relay at said one station which acts if energized upon the reception of a carrier signal to prevent the associated transmitter from being manually rendered active, and means at the other station normally rendering its associated receiver active but capable of at times manually rendering its transmitter active provided no message is being received from said other station, whereby said other station is superior to said one station because said other station can at intervals breakin upon transmission from said one station but said one station cannot break in upon transmission from said other station.

9. In a communication system for transmitting messages in both directions between two stations by the modulation of the same carrier frequency each station having a receiver and a transmitter, means at each station normally rendering said receiver active and said transmitter inactive, manually operable means at each station for at times rendering the associated transmitter active for the thansmission of voice messages, automatic vbreak-inmeans at each .station effectiveto momentarily 4render the associated transmitter inactive at recurring intervals during transmission from that station regardless `of the yoperated condition of its associated manually operable means, and means at each station includinga carrier-responsive `relay associated with the receiver at that station for-preventing the rendering active of the associated transmitter by its associated manually operable means whenever said receiver is receiving a carrier signal, whereby each station may interrupt the transmission from the other station during the break-in interval `in the carrier signal ofsuch other station, and whereby said stations are caused to transmit alternately in opposite directions if both stations are-continuously conditioned to transmit.

10. In a communicaticn system-for transmitting messages by the modulation of a carrier frequency in 4both directions between different stations each of which has `a receiverand a transmitter, a transmit relay acting while deenergized to render the associated receiver activeand the associated transmittel` inactive but effective when energized to render the associated receiver inactive and theassociated,transmitter active, a manually operable'push-button ofthe self-restoring type, a motor driven" timing 4device having a contact intermittently opened'at spaced time intervals when said device is set into operation, a circuit for setting said timing device into operationvwhenever said push button is actuated, checkcontact means closed 4only AWhile said timing device is in operationyand a control circuit for said transmit relay including said contact of said timingv device, a .contact closed when said' push button is operated, and .said check contact'means, whereby said transmit .relaycan render said transmitter effective with brief intervals of rendering said receiver effective as measured by said timing device while said push button is actuated only if said timing device is in operation.

11. In a communication system for transmitting messages by the modulation of a carrier associated transmitter inactive but effective when l energized to render the associated receiver inactive and the associated transmitter active, a manually operable push button, a motor driven timing device having a contact intermittently opened at spaced time intervals when set into operation, a circuit for setting said timing device into operation whenever said push button is actuated, and a control circuit for said transmit relay including said contact of said timing device and a conta-ct closed when said push button is operated, whereby said transmit relay renders said transmitter effective except during spaced brief intervals of rendering said receiver effective as measured by said timing device while said push button is actuated.

12. in a communication system for transmitting messages by the modulation of a carrier frequency, a station having a receiver and a transmitter both being adapted to operate on the same carrier frequency channel, control means at said station for normally rendering the associated receiver effective for the reception of carrier signais, but capable of rendering the associated receiver ineffective to receive carrier signals and the associated tiansmitter effective to transmit acar-rier signalL--when'sucn transmit control means` is manually actuated, vand timing means initiatedby-the manual .actuation of saidicOn-i trol means for-allowing it to ,bez effective to cause the transmission of a carrier signal .by said transmitter for onlya limited time following` the manual actuation `of said .control means, whereby the carrier frequency signal channel cannot -be monopoiized by thisv station.

1'3. in a communication system for the transmissionlof messages by the modulation of the carrier. frequency of an assigned frequency channel, two stations -eachhaving a receiver anda transmitter, control xk'means .at'each station for normally rendering its receiverV effective toreceivefcarrier :signals but manually operableto render-said'transmitter effective to transmit a carrier'signal and at the same time render'said receiver'inelfectivepmeans at each station respon` sive to `the reception of a carrier signal by its receiver1for rendering the associated control means unresponsive ytoY manual actuation so long-asia' carriersignal is being received, and timing means at eachstation initiated by the manual actuation off-:said .control'means atthat station forlallowinrg.- :such .control means to be eiective'foronly alimited time, whereby the control` means isti-neffective torcause transmission at -a station which is receiving` a 4carrier signal but whereby the stationfthen transmitting vcan prevent such receiving :station from being rendered effective 'to transmit for only a limited time.

lli; In .acommunication system for transmitting messages by lthe ymodulation of a carrier frequency, .a istation having areceiver and a 'transmitter, meanswat said station for normally rendering fthe associated .receiver effective to receive carrierrsignalspsaid control means acting when manually actuated to render`r the associated transmitter-effective andthe .associated receiver ineffective, means at said station responsive to the reception of a carrier signal by its receiver for rendering the associated control means incapable of being manually actuated so long as such carrier signal persists, timing means initiated by the manual actuation of said control means for rendering said control means unresponsive to manual control at spaced intervals to render said receiver effective during such intervals, and an indicator controlled by said carrier responsive means to indicate when said control means is unresponsive to manual actuation.

15. In a communication system for transmitting messages by the modulation of a carrier frequency, a station having a receiver and a transmitter, control means at said station for normally rendering the associated receiver effective to receive carrier signals but acting when manually actuated to render said receiver ineffective and the associated transmitter effective for the transmission of a carrier signal that may be modulated with a message, timing means for periodically interrupting the transmission from said station for predetermined short intervals by acting upon said control means, said timing means also acting to render said receiver effective during such intervals, means at said station responsive to the reception of a carrier signal by its associated receiver for rendering said control means unresponsive to manual actuation so long as such carrier signal continues to be received, and an indicator means controlled by said timing means to give an advance warning of an interruption in the transmission With respect to each of said short intervals.

16. In a communication system for transmitting messages by the modulation of a carrier frequency of an assigned frequency channel, a station having a receiver and a transmitter, control means at said station normally acting to render the associated receiver eiective to receive carrier signals, manually operable means for acting upon said control means to cause the associated receiver to be rendered ineffective to receive carrier signals and to cause said associated transmitter to be rendered effective to transmit a carrier signal that may be modulated for the transmission oi a message, means at said station responsive to the reception of a carrier signal by said receiver for preventing said manually operable means from acting upon said control means so long as a carrier signal is being received irrespective of whether such signal is modulated or not, timing means initiated each time said transmitter is rendered effective to transmit a carrier signal for measuring a predetermined limited time in which said transmitter may be rendered effective by said control means, indication means for indicating whenever said control means renders said transmitter effective for the transmission of a carrier signal that may be modulated, another indicator for indicating whenever said carrier responsive means is effective, and a third indicator controlled by said timing means so as to be rendered effective to give an indication shortly before the elapse of said predetermined limited time.

17. In a communication system for transmitting messages by the modulation of a carrier frequency, two stations each having a receiver and a transmitter, a transmit relay at each station normally rendering its associated receiver eiective to receive carrier signals but acting when energized to render its associated transmitter effective to transmit carrier signals and its associated receiver ineffective, a carrier responsive relay at each station responsive to the reception of a carrier frequency by said receiver at that station regardless of any modulation of such carrier frequency, a timing means at each station, said timing means at a station being set into operation each time said transmit relay at that station is energized for repeatedly measuring a predetermined long time followed by a predetermined snort time, and energizing circuit means at each station for said transmit relay at that station, said circuit means including a manually actuatable Contact, a contact opened when said carrier responsive relay is actuated, and a contact opened by said timing means for said predetermined short time at spaced intervals of said predetermined long time, whereby transmission from either station is temporarily interrupted at spaced intervals, whereby either station can effectively break in upon the transmission of the other during any one of said short intervals as measured at such other station, and whereby said two stations are caused to alternately transmit when said manually actuatable contacts are steadily closed at both stations.

WILLIAM D. HAILES.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date Re. 12,073 Shoemaker Jan. 13, 1903 1,945,082 Sandeman et al. Jan. 30, 1934 2,064,639 Whitelock et al. Dec. 15, 1936 '2,115,914 MacKay May 3, 1938 2,199,179 Koch Apr. 30, 1940 2,407,846 OBrien Sept. 17, 1946 

